Decorative material having abrasion resistance

ABSTRACT

A decorative material including a substrate and an abrasion-resistant coating layer formed thereon. The abrasion-resistant coating layer includes spherical particles (A) having an average particle diameter of 3 to 50 micrometers, and a binder (B) including crosslinkable resins. The amount of the spherical particles (A) is from 5% to 50% by weight of the total amount of the components (A) and (B). The hardness of the spherical particles (A) is higher than that of the binder (B). The average particle diameter d (micrometers) of the spherical particles (A) fulfills the following inequality (1): 
     
         0.3t≦d≦3.0t                                  (1) 
    
     wherein &#34;t&#34; is an average thickness (micrometers) of the coating layer. Thus, the relationship between the average thickness of the coating layer and the average particle diameter of the spherical particles is strictly controlled so that a decorative material which is excellent in both flexibility and abrasion resistance (scratch resistance) can be successfully obtained.

TECHNICAL FIELD

The present invention relates to a decorative material whose surface isexcellent in scratch resistance. More specifically, the presentinvention relates to a decorative laminate obtainable by covering thesurface of paper or plastic sheet or film, or the printed surfacethereof, with a coating layer excellent in both abrasion resistance andflexibility.

BACKGROUND OF THE INVENTION

Heretofore, reactive resins such as thermosetting resins orionizing-radiation-curing resins have been used as overcoat materials tocover the surface of paper or plastic sheet or film, or the printedsurface thereof so as to protect such a material from damage by abrasionor scratch.

In order to successfully protect the above-described materials fromdamage by abrasion or scratch, it is necessary to make a resin to beused for coating the materials harder. In order to attain this, it hasbeen necessary to lower the average molecular weight of crosslinkedmolecules of the resin. Consequently, however, the flexibility of theresin itself is lowered, so that the resin layer tends to be crackedwhen the substrate is bent.

DISCLOSURE OF THE INVENTION

We studied overcoat materials capable of forming films which are hardlydamaged by scratch and which have flexibility. As a result, it was foundthat although a coating layer formed by using a composition containingreactive resins to which a predetermined amount of spherical particleshaving a specific average particle diameter are added can show thedesired effects to a certain extent, such a coating layer is stillunsatisfactory. It was also found that it is necessary to furtherspecify the relationship between the average thickness of the coatinglayer and the average particle diameter of the spherical particles andthat a decorative laminate excellent in both flexibility and abrasionresistance can be obtained by strictly controlling this relationship.The present invention has been accomplished on the basis of the abovefindings.

Namely, a decorative material according to the present inventioncomprises a substrate and an abrasion-resistant coating layer formedthereon, and is characterized in that the abrasion-resistant coatinglayer comprises spherical particles (A) having an average particlediameter of 3 to 50 micrometers, and a binder (B) comprisingcrosslinkable resins, that the amount of the spherical particles (A) isfrom 5% to 50% by weight of the total amount of the components (A) and(B), that the hardness of the spherical particles (A) is higher thanthat of the binder (B), and that the average particle diameter d(micrometers) of the spherical particles (A) fulfills the followinginequality (1):

    0.3t≦d≦3.0t                                  (1)

wherein "t" is an average thickness (micrometers) of the coating layer.

BEST MODE FOR CARRYING OUT THE INVENTION Substrate

In the present invention, paper, plastic film or sheet, metallic foil orplate, or the like can be used as the substrate depending on thepurpose. Although either a sheet-like material such as paper, plasticsheet or nonwoven fabric, or a board-like material such as metallicplate, woodboard or plastic board can be used as the substrate, it ispreferable to use a sheet of a flexible material. This is because it ispossible to continuously produce a decorative material when a roll ofsuch a substrate sheet is used in the production process.

In general, in the case where a sheet-like material is used as thesubstrate, the thickness thereof is preferably from 5 to 200micrometers. Further, it is also possible to use, as the substrate, asheet having a rough surface or a three-dimensional pattern.

Specific examples of the paper which can be used as the substrateinclude tissue, craft paper, titanium paper, linter paper, cardboard,plasterboard paper, raw fabric of so-called vinyl wall paper obtained byapplying polyvinyl chloride resin to paper by means of sol coating ordry lamination, high-grade paper, coated paper, art paper, vegetableparchment, glassine paper, animal parchment, paraffin paper and Japanesepaper. In addition, a paper-like sheet can also be used as thesubstrate. Examples of the paper-like sheet include woven or nonwovenfabrics produced by using inorganic fibers such as glass fiber,asbestos, potassium titanate fiber, alumina fiber, silica fiber andcarbon fiber, or organic resins such as polyester and Vinylon.

Examples of the plastic sheet which can be used as the substrate includesingle layers or composites of films or sheets of synthetic resins, forinstance, polyolefin resins such as polyethylene, polypropylene andpolymethylpentene, vinyl resins such as polyvinyl chloride,polyvinylidene chloride, polyvinyl alcohol, vinyl chloride-vinyl acetatecopolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcoholcopolymer and Vinylon, polyester resins such as polyethyleneterephthalate, polybutylene terephthalate and polyethylenenaphthalate-isophthalate copolymer, acrylic resins such as polymethylmethacrylate, polyethyl methacrylate, polyethyl acrylate and polybutylacrylate, polyamides such as nylon 6 and nylon 66, cellulose resins suchas cellulose triacetate and cellophane, polystyrene, polycarbonate,polyallylate and polyimide. Further, examples of the metal which is usedas metallic foil include aluminum, stainless steel, iron and copper.

Examples of the board which can be used as the substrate includewoodboards such as veneer, plywood, particle board and MDF (mediumdensity fiber board), plaster-type boards such as plaster and plasterslug boards, cement boards such as calcium silicate, asbestos slate,light-weight expanded concrete and blow-extruded cement boards,fiber-cement boards such as pulp-cement, asbestos-cement andwood-chip-cement boards, ceramic boards such as earthenware, porcelain,stoneware, terra-cotta, glass and enameled ware boards, metallic platessuch as iron, zinc-plated steel, polyvinyl-chloride-sol-coated steel,aluminum and copper plates, thermoplastic resin boards such aspolyolefin resin, acrylic resin, ABS and polycarbonate boards,thermosetting resin boards such as phenolic resin, urea resin,unsaturated polyester, polyurethane resin, epoxy resin and melamineresin boards, and other resin boards, for instance, so-called FRP boardswhich are obtained by impregnating various fibrous substrates such asnonwoven fabric of glass fiber, cloth and paper, with a resin such asphenolic, urea, unsaturated polyester, polyurethane, epoxy, melamine ordiallyl phthalate resin.

It is also possible to use, as the substrate, a composite substratewhich can be obtained by laminating two or more of the above-mentionedvarious substrates by any known means, for instance, by the use of anadhesive agent, or by effecting thermal fusion.

Spherical Particles

The spherical particles (A) for use in the present invention areparticles in the shape of a sphere or of one similar to it. Preferableexamples of the spherical particles include fused alumina, aluminaproduced by the Bayer process, zirconia, titania, and eutectic mixturesthereof, which have a Knoop hardness of 1,300 kg/mm² or more. Of these,those spherical particles which have a Knoop hardness of 1,800 kg/mm² ormore are preferred, and fused alumina can be mentioned as a specificexample of such particles.

The "Knoop hardness" as used herein is an indentation microhardnessmeasured by using a Knoop indenter; it is a value obtained by dividingthe applied load with which a rhombic indentation is formed on thesurface of a sample, by the projected area of the indentation computedfrom the long diagonal of the permanent indentation. The method formeasuring the Knoop hardness is described in ASTM C-849. As a method forshaping inorganic particles into spherical ones, it is possible to applya method in which the above-described inorganic material in anindeterminate form is ground, and melted in a high-temperature oven at atemperature above the melting point thereof, thereby obtaining sphericalparticles by utilizing the surface tension; or a method in which theabove-described inorganic material is melted at a high temperature abovethe melting point thereof, and the melt is sprayed to obtain sphericalparticles.

The content of the spherical particles in a composition used for formingthe abrasion-resistant coating layer of the present invention isgenerally from 5 to 50% by weight, preferably from 10 to 40% by weight.

When the content of the spherical particles is less than 5% by weight,the scratch resistance of the coating layer is insufficient. On theother hand, when the content of the spherical particles is more than 50%by weight, the binder effects of the crosslinkable resins cannot befully obtained, and the coating layer has lowered flexibility.

The average particle diameter of the spherical particles is, in general,from 3 to 50 micrometers, preferably from 8 to 40 micrometers. Whenspherical particles having an average particle diameter of less than 3micrometers are used, an opaque coating layer is obtained, so that suchan average particle diameter is unfavorable. On the other hand, theaverage particle diameter of more than 50 micrometers is much largerthan the thickness of a coating layer formed by using a typical coatingcomposition. The surface smoothness of the coating layer is thusimpaired.

When the composition of the present invention is coated onto thesubstrate, the thickness of the resulting coating layer and theabove-described average particle diameter d are required to fulfill thefollowing inequality (1):

    0.3t≦d≦3.0t                                  (1)

wherein "t" is an average thickness (micrometers) of the coating layer.

When the average particle diameter is in excess of 3.0 t, the particlesprotrude from the surface of the coating layer, so that the coatinglayer has a poor appearance. On the other hand, when the averageparticle diameter is less than 0.3 t, the coating layer has impairedscratch resistance, so that such an average particle diameter isunfavorable.

With respect to the spherical particles, more specific explanation willbe given below.

It is enough for the spherical particles to have smooth curved surfaces,like perfectly-round particles, elliptical particles obtainable byflattening round particles, and particles which are similar toperfectly-round or elliptical particles in shape. The sphericalparticles are preferably those which have neither projection nor edge onthe surfaces thereof, that is, so-called cutting-edge free particles.The spherical particles can greatly improve the abrasion resistance ofthe surface resin layer itself, as compared with particles in anindeterminate form made of the same material, and, at the same time,produce the following characteristic effects: the spherical particles donot wear a coating applicator used; the hardened coating layer also doesnot wear those things which are brought into contact with the coatinglayer; and the coating layer has improved transparency. These effectsare particularly obtained when the spherical particles have no cuttingedge.

It is preferable that the hardness of the material used for producingsuch spherical particles be higher than that of the crosslinkable resin,which will be described later, to be used. Particles of either aninorganic or organic resin can be used. The hardness of the sphericalparticles and that of the crosslinkable resin can be determined by meansof the Mohs hardness test, the Vickers hardness test or the like. Forexample, when these hardnesses are expressed in Mohs scale, it ispreferable that the difference between these hardnesses be 1 or more.The "Mohs hardness" as used herein is based on the conventionaldefinition of the Mohs hardness, that is, the value obtained bycomparison with the following ten selected minerals:

1: talc; 2: gypsum; 3: calcite; 4: fluorite; 5: apatite; 6: orthoclase;7: quartz; 8: topaz; 9: corundum; and 10: diamond.

Specifically, particles of an inorganic material such as alpha-alumina,silica, chromium oxide, iron oxide, diamond or graphite, or organicresin particles, for instance, beads of a synthetic resin such ascrosslinked acrylic resin can be used as the spherical particles.Particularly preferable spherical particles are spherical alpha-aluminaparticles. This is because alpha-alumina has an extremely high hardnessand can impart high abrasion resistance to the resulting coating layer,and because alpha-alumina which is spherical in shape is readilyobtainable.

Spherical alpha-alumina with decreased cutting edges can be obtained, asdescribed in Japanese Laid-Open Patent Publication No. 55269/1990, byadding a small amount of a hardener or crystallizing agent such asalumina hydrate, a halide or boron compound to fused or sintered aluminawhich has been ground, and thermally treating the mixture at atemperature of 1,400° C. or higher for two hours or longer. Sphericalaluminas of this type, having various average particle diameters arecommercially available under the trademark of "Spherical Alumina AS-10,AS-20, AS-30, AS-40 and AS-50" from Showa Denko K.K.

The spherical particles can be subjected to surface treatment. Forinstance, when the spherical particles are treated with a fatty acidsuch as stearic acid, the dispersibility of the particles is improved.Further, when the spherical particles are surface-treated with a silanecoupling agent, the adhesion between the particles and the crosslinkableresin used as the binder, and the dispersibility of the particles in thecoating composition are improved. Examples of the silane coupling agentinclude alkoxysilanes containing in the molecules thereof aradically-polymerizable unsaturated bond such as vinyl or methacryl, andalkoxysilanes containing in the molecules thereof a functional groupsuch as epoxy, amino or mercapto. It is preferable to suitably selectthe type of the radically-polymerizable unsaturated bond or functionalgroup contained in the silane coupling agent, depending on the type ofthe crosslinkable resin which is used along with the sphericalparticles. For example, in the case where an ionizing-radiation-curingresin such as (meth)acrylate is used as the crosslinkable resin, analkoxysilane having a radically-polymerizable unsaturated bond is used;and when a two-pack hardening urethane resin is used, an alkoxysilanehaving epoxy or amino group is used. Specific examples of thealkoxysilanes include those which contain in the molecules thereof aradically-polymerizable unsaturated bond, such asgamma-methacryloxypropyl trimethoxysilane,gamma-methacryloxy-propylmethyl dimethoxysilane,gamma-methacryloxypropyldimethyl methoxysilane,gamma-methacryloxypropyldimethyl ethoxysilane, gamma-acryloxypropyltrimethoxysilane, gamma-acryloxypropyl-methyl dimethoxysilane,gamma-acryloxypropyldimethyl methoxysilane, gamma-acryloxypropyltriethoxysilane, gamma-acryloxypropylmethyl diethoxysilane,gamma-acryloxypropyldimethyl ethoxysilane and vinyl triethoxysilane; andthose which contain in the molecules thereof a functional group such asepoxy, amino or mercapto.

There is no particular limitation on the method for surface-treating thespherical particles by using a silane coupling agent, and anyconventionally known method can be adopted. Examples of such a methodinclude a dry method in which a predetermined amount of a silanecoupling agent is sprayed over the spherical particles with vigorousstirring; and a wet method in which after the spherical particles aredispersed in a solvent such as toluene, a predetermined amount of asilane coupling agent is added to the dispersion to allow to react theparticles with the coupling agent. The preferable amount (the amountrequired) of the silane coupling agent to be used for treating thespherical particles is such that the minimum area of the sphericalparticles covered with the silane coupling agent can be 10 or more for100 of the specific surface area of the spherical particles. It is notso effective to use a silane coupling agent in such an amount that theminimum area of the spherical particles covered with the silane couplingagent becomes less than 10 for 100 of the specific surface area of thespherical particles.

Binder

A thermosetting resin or an ionizing-radiation-curing resin can be usedas the crosslinkable resin (reactive resin) to be comprised in thebinder (B) for use in the present invention.

A conventionally known thermosetting resin can be used for the binder.Examples of such a resin include two-pack urethane, epoxy, alkyd andunsaturated polyester resins.

Examples of the two-pack urethane resin include those which are obtainedby blending a first liquid comprising such a polyol compound thatcontains in the molecular structure thereof at least two hydroxyl groupson the average, with a second liquid comprising a polyisocyanatecompound so that the equivalent ratio of the hydroxyl groups to theisocyanate groups will be from 0.7 to 1.5.

Examples of the above-mentioned epoxy resin include those which areobtained by blending an epoxy resin containing in the molecularstructure thereof at least two epoxy groups on the average, with a mono-or polyamine containing in one molecule thereof at least three activehydrogens which can react with the epoxy groups so that the equivalentratio of the epoxy groups in the epoxy resin to the active hydrogens inthe mono- or polyamine will be from 0.7 to 1.5.

There can be mentioned, as the ionizing-radiation-curing resin used asthe binder component, those compounds which contain in the molecularstructure thereof one or more radically-polymerizable double bonds.Specific examples of such compounds include unsaturated polyester resin,compounds having (meth)acryloyl group monofunctional (meth)acrylate,polyfunctional (meth)acrylate, urethane (meth)acrylate, polyester(meth)acrylate, epoxy (meth)acrylate, etc.!, vinyl compounds styrene,divinylbenzene, etc.!, allyl compounds diallylphthalate, etc.!, andmixtures of two or more of these compounds.

The ionizing-radiation-curing resin is more preferable as the binderresin for use in the present invention, and a polyether urethane(meth)acrylate represented by the following general formula (2) isparticularly preferred:

    CH.sub.2 =C(R.sup.1)--COOCH.sub.2 CH.sub.2 --OCONH--X--NHCOO-- --CH(R.sup.2)--CH.sub.2).sub.n --O--!.sub.m --CONH--X--NHCOO--CH.sub.2 CH.sub.2 OCOC(R.sup.1)═CH.sub.2( 2)

wherein R¹ and R² each represent hydrogen or methyl group, X isdiisocyanate radical, n is an integer of 1 to 3, and m is an integer of6 to 60.

A conventionally known diisocyanate can be used for preparing the abovepolyether urethane (meth)acrylate. Specific examples of the diisocyanateinclude isophorone diisocyanate, dicyclohexylmethane diisocyanate,hexamethylene diisocyanate, diphenylmethane diisocyanate and tolylenediisocyanate.

Examples of the polyether diol used for preparing the above polyetherurethane (meth)acrylate include polyoxypropylene glycol, polyoxyethyleneglycol and polyoxytetramethylene glycol, having a molecular weight of500 to 3,000.

In the case where the polyether urethane (meth)acrylate represented bythe above general formula (2) is used as the binder, the amount thereofis preferably 10% by weight or more of the total weight of the binder.When less than 10% by weight of this resin is used, the binder resinitself has lowered flexibility, so that the resulting coating layertends to be cracked when the substrate is bent.

To cure the composition of the present invention by the irradiation ofionizing radiation, ultraviolet rays or electron beam can be used as theionizing radiation.

In the case where the curing of the composition of the present inventionis effected by using ultraviolet rays, a conventionally knownultraviolet irradiator equipped with a high-pressure mercury vapor lamp,a metallic halide lamp or the like can be used.

The irradiance of ultraviolet rays for curing the composition of thepresent invention is preferably from 50 to 1,000 mJ/cm². When theirradiance of ultraviolet rays is less than 50 mJ/cm², the compositioncannot be fully cured. On the other hand, when the irradiance is inexcess of 1,000 mJ/cm², there is such a possibility that the curedcoating layer undergoes yellowing and degradation.

When the curing of the composition of the present invention is effectedby the use of electron beam, a conventionally known electron beamirradiator can be used.

In this case, the irradiance of electron beam is preferably from 1 to 20Mrad. When the irradiance of electron beam is less than 1 Mrad, thecomposition cannot be fully cured. On the other hand, when theirradiance is in excess of 10 Mrad, there is such a possibility that thecured coating layer or the substrate (paper, plastic sheet or film, orthe like) is damaged, and degraded.

In the present invention, the average molecular weight of crosslinkedmolecules of the binder resins after reacted is generally in the rangeof 180 to 1,000, more preferably from 200 to 800, and most preferablyfrom 250 to 500.

When the average molecular weight of crosslinked molecules is less than180, the binder resin itself has lowered flexibility, so that theresulting coating layer tends to be cracked when the substrate is bent.On the other hand, when the average molecular weight of crosslinkedmolecules is in excess of 1,000, the binder resin itself becomesexcessively soft, so that it cannot fully retain therein the sphericalparticles. The resulting coating layer is thus poor in scratchresistance.

The "average molecular weight of crosslinked molecules" as used hereinmeans a value represented by m/ 2×(f-1)!, in which "f" is an averagenumber of polymerizable functional groups contained in crosslinkableresins, and m is an average molecular weight of the crosslinkableresins.

Moreover, the average molecular weight of crosslinked molecules can alsobe represented by the following equation:

    Average Molecular Weight of Crosslinked Molecules=Total Molecular Weight/Number of Crosslinked Points, wherein the total molecular weight is Σ

    ((number of moles of each component blended)×(molecular weight of each component)) and the number of crosslinked points is Σ {(number of functional groups contained in each component-1)×2}×(number of moles of each component)!.

The average molecular weights of crosslinked molecules obtained from theabove two equations agree with each other.

The results of experiments carried out in order to examine therelationship between the abrasion resistance and the flexibility of acoating layer with the average molecular weight of crosslinked moleculesof crosslinkable resins changed are shown in the below Table 1. The datashown in Table 1 were obtained in the following manner: urethaneacrylate oligomer and two different types of acrylate monomers were usedas the crosslinkable resins, and the average molecular weight ofcrosslinked molecules was adjusted by changing the blend ratio of thesecrosslinkable resins. A composition containing the crosslinkable resins,and, as the spherical particles, spherical alpha-alumina having anaverage particle diameter of 30 micrometers in an amount of 11 parts byweight for 100 parts by weight of the crosslinkable resins was coatedonto a substrate in an amount of 25 g/m² to form a coating layer. Thecoating layer was cured, and the abrasion resistance and the flexibilityof the cured coating layer were compared. The abrasion resistance testwas carried out in accordance with JIS K6902, and the abrasionresistance was expressed in the number of tests carried out until thethickness of the resin layer was reduced to half. The flexibility of thecrosslinkable resin layer after cured was rated according to thefollowing standard:

⊚: the flexibility is very high;

◯: the flexibility is good;

Δ: the flexibility is low; and

X: the flexibility is considerably low.

It is noted that in Experiment No. 6, conventional alpha-alumina withedges in an indeterminate form, having an average particle diameter of30 micrometers was used, instead of the spherical particles, in the sameamount as in Experiments 1 to 5. In the above-described resin system,although it is possible to vary the average molecular weight ofcrosslinked molecules between 180 and 1,000, a preferable range thereofis from 200 to 800. Further, when a flexible substrate is used, it ismore preferable to use a resin system whose average molecular weight ofcrosslinked molecules is from 300 to 700. When such a resin system isused, a decorative material which is more excellent in both flexibilityand abrasion resistance can be obtained.

                  TABLE 1    ______________________________________    Experiment No.                1      2      3     4     5     6    ______________________________________    Average Molecular                700    520    330   250   150   520    Weight of Crosslinked    Molecules    Result of Abrasion                500    800    1500  2500  3000  200    Resistance Test    Flexibility ⊚                       ∘                              ∘                                    Δ                                          x     ∘    ______________________________________

In order to use the composition of the present invention for coating, itis preferable that the viscosity of the composition be low from theoperational point of view. The viscosity of the composition at anoperating temperature is preferably 500 centipoises or lower, morepreferably 200 centipoises or lower. When the viscosity of thecomposition is higher than 500 centipoises, the operatingcharacteristics are poor, and there may be a case where a coating layerhaving a smooth surface cannot be obtained.

At the time when the composition of the present invention is used forcoating, it is preferable to use, in order to control the viscosity ofthe composition, one or more solvents capable of dissolving therein thebinder, having a boiling point at normal pressure of 70 to 150° C., inan amount of 40% by weight or less of the total amount of the components(A) and (B).

When the amount of the solvent(s) used is in excess of 40% by weight,the production efficiency is lowered, so that such an amount isunfavorable.

A solvent which is conventionally used in paints, inks or the like canbe used as the above-described solvent. Specific examples of such asolvent include aromatic hydrocarbons such as toluene and xylene,ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone andcyclohexane, acetic acid esters such as ethyl acetate, isopropyl acetateand amyl acetate, alcohols such as methyl alcohol, ethyl alcohol andisopropyl alcohol, ethers such as dioxane, tetrahydrofuran anddiisopropyl ether, and mixtures of two or more of these solvents.

Additives which are conventionally added to paints or inks, such asthermosetting catalysts, photopolymerization initiators, anti-foamagents, leveling agents and coupling agents can be further incorporatedinto the binder for use in the present invention, when necessary.

Examples of the thermosetting catalyst which is used in the presentinvention when the binder resin is alkyd or unsaturated polyester resininclude peroxides such as tert-butyl peroxybenzoate, benzoyl peroxideand methyl ethyl ketone peroxide, and azo compounds such asazobisisobutyronitrile and azobisisovaleronitrile.

Examples of the thermosetting catalyst which is used in the presentinvention when the binder is epoxy resin include imidazoles such as2-methyl-4-ethylimidazole, and phenols such as phenol, cresol andbisphenol A.

Examples of the thermosetting catalyst which is used in the presentinvention when the binder is two-pack urethane resin include dibutyltindilaurate, tin octoate and triethylamine.

The amount of the thermosetting catalyst which is used when necessary isgenerally 10% by weight or less, preferably 5% by weight or less of theweight of the binder.

Preferable examples of the photopolymerization initiator which is usedin the present invention when the binder resin is an ultraviolet-curingresin include benzoin alkyl ether, benzyldimethyl ketal,1-hydroxycyclohexyl phenyl ketone,2-hydroxy-2-methyl-1-phenylpropane-1-one, benzophenone, methylbenzoylformate and isopropyl thioxantone.

The amount of the photopolymerization initiator is generally 20% byweight or less, preferably 6% by weight or less of the weight of thebinder.

Coloring agents such as dyes and pigments, known fillers such asflatting agents and bulk fillers, for example, CaCo₃, BaSO₄ and nylonresin beads, and other additives can also be added to the coatingcomposition comprising the above-described crosslinkable resins as thebinder, and the spherical particles.

Method of Coating

A method for forming an abrasion-resistant resin layer on the surface ofa substrate by the use of the above-described coating composition willnow be explained.

An abrasion-resistant resin layer can be formed either by a directcoating method (1) in which the coating composition is directly coatedonto the surface of a substrate; or by a transfer coating method (2) inwhich after an abrasion-resistant resin layer is formed on the surfaceof a substrate having release properties, the resin layer is transferredto the surface of a desired substrate. In general, when a material intowhich the coating composition does not penetrate is used as thesubstrate, either one of the above-described methods (1) and (2) can beused. It is however preferable to adopt the above method (2) when amaterial into which the coating composition penetrates or which has arough surface is used as the substrate, and to obtain a coating layerhaving a uniform thickness, or to evenly impart abrasion resistance tothe coating layer by applying ionizing radiation of a uniform intensity.

Examples of the above-described direct coating method (1) includegravure coating, gravure reverse coating, gravure offset coating,spinner coating, roll coating, reverse roll coating, kiss-roll coating,wheeler coating, dip coating, solid coating by using a silk screen, wirebar coating, flow coating, comber coating, pour coating, brush coatingand spray coating. Of these, gravure coating is preferred.

The transfer coating method (2) includes the following methods (a) to(d), in which a coating layer is firstly formed on a thin sheet (film)substrate, cured by crosslinking reaction, and then transferred to thesurface of a desired substrate. The following means can be utilized toeffect the transfer coating method; the lamination method ((a) or (b))in which the coating layer formed by the coating composition is adhered,along with the thin substrate, to a three-dimensional object; or thetransfer method (c) in which after a transfer sheet prepared by forminga coating layer, and, if necessary, an adhesive layer on a substratesheet having release properties and curing the coating layer bycrosslinking reaction is adhered to a three-dimensional object with thecoating layer faced the surface of the object, only the substrate sheetis released from the transfer sheet. It is noted that any of theabove-described direct coating methods can be employed when anabrasion-resistant resin layer is firstly formed on a thin sheetsubstrate in the transfer coating method.

(a) Injection molding-transfer method, as n Japanese Patent PublicationsNos. 42080/1990 and 19924/1992; or injection molding-lamination methodas disclosed in Japanese Patent Publication No. 19132/1975.

(b) Vacuum molding-transfer method as disclosed in Japanese Laid-OpenPatent Publications Nos. 288214/1992 and 57786/1993; or vacuummolding-lamination method as disclosed in Japanese Patent PublicationNo. 45768/1981.

(c) Wrapping-transfer or wrapping-lamination method as disclosed inJapanese Patent Publications Nos. 51900/1984, 5895/1986 and 2666/1991.

(d) V-notch processing-lamination method as disclosed in JapaneseUtility Model Publication No. 15-31155, or V-notch processing-transfermethod as disclosed in Japanese Patent Publication No. 7866/1981.

A method comprising the following sequential steps (A) to (D) (describedin Japanese Laid-Open Patent Publication No. 26673/1990) can also beused as one of the above-mentioned transfer coating methods (2) when anionizing-radiation-curing resin is used as the crosslinkable resin:

(A) the step of coating a liquid ionizing-radiation-curing resincomposition, which is not yet cured, onto a non-absorbent syntheticresin sheet having release properties;

(B) the step of laminating the resin sheet to a substrate with thecoating layer formed by the ionizing-radiation-curing resin compositionfaced the surface of the substrate;

(C) the step of irradiating ionizing radiation to the coating layerformed by the ionizing-radiation-curing resin composition to cure thecoating layer by crosslinking; and

(D) the step of releasing the synthetic resin sheet.

In the case where an ionizing-radiation-curing resin diluted with asolvent is used in the above process, the step of evaporating thesolvent is provided between the steps (A) and (B). According to theabove process, even when a material having high permeability such aspaper is used as the substrate, so-called "strike-through", a phenomenonthat the resin goes through the substrate to the reverse side thereof,can be fully prevented, and an excellent abrasion-resistant resin layercan be easily formed on the surface of the substrate.

In the case where an ionizing-radiation-curing resin is used as thecrosslinkable resin, the following ionizing-radiation irradiator is usedfor curing the resin: in order to irradiate ultraviolet rays, anirradiator having, as a light source, an ultra-high-pressure mercuryvapor lamp, a high-pressure mercury vapor lamp, a low-pressure mercuryvapor lamp, carbon arc, a black-light lamp, a metallic halide lamp orthe like is used; and in order to irradiate electron beam, any ofvarious electron beam accelerators such as a Cockcroft-Waltonaccelerator, a van de Graaff accelerator, a resonant-transformer-typeaccelerator, an insulating-core-transformer-type accelerator, and alinear, dynamitron or high-frequency accelerator is used. When electronbeam is irradiated, electrons with an energy of, in general, 100 to1,000 keV, preferably 100 to 300 keV are irradiated in an irradiated ofapproximately 0.1 to 30 Mrad.

Further, when a thermosetting resin is used as the crosslinkable resin,the coating composition can be heated after the step of coating in orderto accelerate the curing reaction of the thermosetting resin. Ingeneral, the heating time is approximately 1 to 5 days at 40 to 60° C.when isocyanate-curing unsaturated polyester resin or polyurethane resinis used, and approximately 1 to 300 minutes at 80 to 150° C. whenpolysiloxane resin is used.

The decorative material of the present invention can be composed only ofthe substrate and the abrasion-resistant resin layer formed thereon.However, it is also possible to provide a pattern on the surface of thesubstrate, and to form the abrasion-resistant resin layer on thepatterned surface. The pattern can be provided by means of printing,using a printing ink containing a vehicle to which known colorants suchas pigments or dyes, extender pigments, solvents, stabilizers,plasticizers, catalysts and curing agents are suitably added, ifnecessary. A resin having required physical properties and printability,suitably selected from thermoplastic, thermosetting andionizing-radiation-curing resins and the like is used as theabove-described vehicle. Further, any of those organic or inorganicpigments which are conventionally used can be employed as the pigment. Aliquid solvent which can dissolve or disperse therein the resin used asthe vehicle, the coloring agents such as pigments and other additivesand which has proper drying characteristics is used as the solvent fordilution. In general, it is preferable, from the viewpoint ofsolubility, to select a liquid solvent whose solubility parameter isalmost equal to that of the vehicle. A pattern (for example, a patternof wood grain, texture, figures, letters or the like) can be provided onthe surface of the substrate either partially or entirely. For example,when it is required to emphasize a certain part of a pattern (forexample, a glossy part of a wood grain pattern), the pattern is providedpartially. In order to entirely give a pearly appearance or Moirepattern, a solid pattern is provided entirely.

Further, it is also possible to carry out the following procedure in thepresent invention: a resin layer is provided on the surface of asubstrate, and a desired pattern is provided by forming indentations inthe surface resin layer; the indentations formed in the surface resinlayer are filled with a conventional coloring ink by means of wiping toform a wiped-ink layer; and an abrasion-resistant resin layer is thenformed on top of the wiped-ink layer. Furthermore, it is also possibleto directly provide the pattern-wise indentations and wiped-ink layer onthe surface of the substrate.

The following process is used for forming a wiped-ink layer, which is alayer of a coloring ink filled in indentations, in the production of adecorative material. Namely, after a coating composition containing acoloring ink is coated onto the entire surface of a substrate having asurface resin layer in which an embossed pattern has been provided by aconventional embossing technique, the surface of the surface resin layercoated with the coating composition is wiped by a doctor blade, an airknife, a roller whose surface is covered with sponge, or the like,whereby the coating composition deposited on the projected parts of theembossed pattern is removed, and a coloring ink layer is thus formed bythe ink remaining only in the indentations. Since a colored coatingcomposition is used in this wiping process, the vessels of wood graincan be excellently reproduced when a pattern of wood grain is providedby forming indentations. In this case, a transparent resin is used forforming the surface resin layer.

The decorative material of the present invention, having abrasionresistance can be used for various purposes; for instance, it is usefulfor decorating the surfaces of buildings, vehicles, ships, furnitures,musical instruments, cabinets and the like, and also for decoratingwrapping materials. The decorative material of the present invention isparticularly suitable in the fields where abrasion resistance isrequired. When the decorative material of the present invention isapplied to the above-described uses, it can be laminated on the surfaceof any of the above objects to be decorated by one of various means suchas the methods (a) to (d), which have been previously described in orderto explain the transfer coating method.

The present invention will now be explained more specifically byreferring to the following examples. However, the present invention isnot limited by these examples. In the examples, the unit "part(s)" means"part(s) by weight".

Example 1

    ______________________________________    Bisphenol A epoxy resin 70 parts     "Epicoat 828" manufactured by    Yuka Shell Epoxy Kabushiki Kaisha!    1,6-Hexamethylene glycol diglycidyl ether                            14 parts     "SR-16H" manufactured by Sakamoto    Yakuhin Kogyo, Co., Ltd.!    Spherical alumina having an average                            15 parts    particle diameter of 30 micrometers and    a Knoop hardness of 2,800     "Alumina Beads CB-A30S" manufactured    by Showa Denko K.K.!    Thixotropic agent  "Aerosil 200"                            0.5 parts    manufactured by Nippon Aerosil Co., Ltd.!    Anti-settling agent  "Orben" manufactured                            0.5 parts    by Shiraishi Kogyo Kaisha, Ltd.!    ______________________________________

The above components were uniformly mixed by a planetary mixer. Theresulting mixture is referred to as "Base 1". 17 parts of m-xylylenediamine and 20 parts of toluene were uniformly mixed with 100 parts ofBase 1. The viscosity of the resulting mixture was 400 centipoises.

This mixture was coated onto printed paper to form a coating layer sothat the thickness of the coating layer would be 25 micrometers whendried. The coating layer was then cured at 40° C. for 20 minutes. Taberabrasion test was carried out for this coated paper in accordance withJIS K-6902. As a result, the abrasion loss at a number of revolutions of200 was 30 mg.

Production Example 1

In a glass reactor equipped with a dropping funnel, a thermometer, areflux condenser and a stirring rod, 1,000 parts of polytetramethyleneglycol having a molecular weight of 1,000 and 444 parts of isophoronediisocyanate were charged, and reaction was carried out at 120° for 3hours. The reaction mixture was then cooled to a temperature of 80° C.or lower. To this mixture was added 232 parts of 2-hydroxyethylacrylate, and reaction was carried out at 80° C. until the isocyanategroup disappeared. The product of this reaction is referred to as"Urethane acrylate 1".

Example 2

    ______________________________________    Urethane acrylate 1     20 parts    Bisphenol A (EO).sub.4 diacrylate                            20 parts    Phenol (EO).sub.2 acrylate                            20 parts    Spherical alumina having an average particle                            15 parts    diameter of 30 micrometers and a Knoop    hardness of 2,800     "Alumina Beads CB-A30S" manufactured    by Showa Denko K.K.!    Photopolymerization initiator                            3 parts     "Darocure 1173" manufactured by Merck!    Thixotropic agent  "Aerosil 200"                            0.5 parts    manufactured by Nippon Aerosil Co., Ltd.!    Toluene                 5 parts    ______________________________________

The above components were uniformly mixed. The viscosity of the mixturewas 440 centipoises. The average molecular weight of crosslinkedmolecules of the reactive resins was 272. The mixture was coated ontoprinted paper to form a coating layer so that the thickness of thecoating layer would be 25 micrometers when dried, and 150 mJ/cm² ofultraviolet rays were irradiated to the coating layer. Taber abrasiontest was carried out for this coated paper in the same manner as inExample 1. As a result, the abrasion loss was 25 mg.

Example 3

    ______________________________________    Urethane acrylate 1     20 parts    Trimethylolpropane triacrylate                            20 parts    Bisphenol A (EO).sub.4 diacrylate                            10 parts    Phenol (EO).sub.2 acrylate                            30 parts    Spherical alumina having an average particle                            15 parts    diameter of 30 micrometers and a Knoop    hardness of 2,800     "Alumina Beads CB-A20S" manufactured    by Showa Denko K.K.!    Thixotropic agent  "Aerosil 200"                            0.5 parts    manufactured by Nippon Aerosil Co., Ltd.!    ______________________________________

The above components were uniformly mixed. The viscosity of the mixturewas 740 centipoises. The average molecular weight of crosslinkedmolecules of the reactive resins was 287. The mixture was coated ontoprinted paper to form a coating layer so that the thickness of thecoating layer would be 20 micrometers when dried, and 3 Mrad of electronbeam was irradiated to the coating layer. Taber abrasion test wascarried out for this coated paper in the same manner as in Example 1. Asa result, the abrasion loss was 18 mg.

Example 4

    ______________________________________    Urethane acrylate 1       14    parts    Pentaerythritol triacrylate                              10    parts    Bisphenol A (EO).sub.4 diacrylate                              30    parts    Neopentyl glycol (PO).sub.2 diacrylate                              12    parts    2-Hydroxy-3-phenoxypropyl acrylate                              11    parts    2-Acryloyloxyethyl phosphate                              1     part    Bis(methacryloxypropyl)poly(dimethylsiloxane)                              3     parts    Spherical alumina having an average particle                              22    parts    diameter of 25 micrometers and a Knoop    hardness of 2,800     "Harimick AX-25" manufactured    by Micron Co., Ltd.!    Thixotropic agent  "Aerosil 200"                              0.5   parts    manufactured by Nippon Aerosil Co., Ltd.!    Ethyl acetate             10    parts    ______________________________________

The above components were uniformly mixed. The viscosity of the mixturewas 440 centipoises.

The mixture was coated onto printed paper to form a coating layer sothat the thickness of the coating layer would be 25 micrometers whendried, and 5 Mrad of electron beam was irradiated to the coating layer.Taber abrasion test was carried out for this coated paper in the samemanner as in Example 1. As a result, the abrasion loss was 15 mg.

Comparative Example 1

    ______________________________________    Urethane acrylate 1     20 parts    Trimethylolpropane triacrylate                            20 parts    Bisphenol A (EO).sub.4 diacrylate                            20 parts    Phenol (EO).sub.2 acrylate                            20 parts    Photopolymerization initiator                            3 parts     "Darocure 1173" manufactured by Merck!    Thixotropic agent  "Aerosil 200"                            0.5 parts    manufactured by Nippon Aerosil Co., Ltd.!    Toluene                 5 parts    ______________________________________

The above components were uniformly mixed. The viscosity of the mixturewas 400 centipoises.

The mixture was coated onto printed paper to form a coating layer sothat the thickness of the coating layer would be 25 micrometers whendried, and 150 mJ/cm² of ultraviolet rays were irradiated to the coatinglayer. Taber abrasion test was carried out for this coated paper in thesame manner as in Example 1. As a result, the coating layer wascompletely abraded, and even the substrate was found to be worn away.

Comparative Example 2

    ______________________________________    Urethane acrylate 1     20 parts    Trimethylolpropane triacrylate                            20 parts    Bisphenol A (EO).sub.4 diacrylate                            10 parts    Phenol (EO).sub.2 acrylate                            30 parts    Thixotropic agent  "Aerosil 200"                            0.5 parts    manufactured by Nippon Aerosil Co., Ltd.!    ______________________________________

The above components were uniformly mixed. The viscosity of the mixturewas 720 centipoises.

The mixture was coated onto printed paper to form a coating layer sothat the thickness of the coating layer would be 20 micrometers whendried, and 3 Mrad of electron beam was irradiated to the coating layer.Taber abrasion test was carried out for this coated paper in the samemanner as in Example 1. As a result, the coating layer was completelyabraded, and even the substrate was found to be worn away.

Comparative Example 3

    ______________________________________    Urethane acrylate 1      14 parts    Pentaerythritol triacrylate                             10 parts    Bisphenol A (EO).sub.4 diacrylate                             30 parts    Neopentyl glycol (PO).sub.2 diacrylate                             12 parts    2-Hydroxy-3-phenoxypropyl acrylate                             11 parts    Bis(methacryloxypropyl)poly(dimethylsiloxane)                             3 parts    Thixotropic agent  "Aerosil 200"                             0.5 parts    manufactured by Nippon Aerosil Co., Ltd.!    Ethyl acetate            10 parts    ______________________________________

The above components were uniformly mixed. The viscosity of the mixturewas 400 centipoises.

The mixture was coated onto printed paper to form a coating layer sothat the thickness of the coating layer would be 25 micrometers whendried, and 5 Mrad of electron beam was irradiated to the coating layer.Taber abrasion test was carried out for this coated paper in the samemanner as in Example 1. As a result, the coating layer was completelyabraded, and even the substrate was found to be worn away. In thedecorative material according to the present invention, the coatinglayer is formed by using a composition prepared by adding a specificamount of spherical particles whose average particle diameter is in aspecific range to crosslinkable resins, and the relationship between theaverage thickness of the coating layer and the average particle diameterof the spherical particles is also specified. The coating layer istherefore excellent in both scratch resistance and flexibility, and thedecorative material having the coating layer is excellent in surfacetransparency and surface smoothness. The decorative material of thepresent invention is scarcely damaged by abrasion or scratch, and isflexible, so that the coating layer is not cracked even when thesubstrate is bent. In addition, the decorative material of the inventionalso has a good appearance.

We claim:
 1. A decorative material comprising:a substrate; and anabrasion-resistant coating layer formed on said substrate, saidabrasion-resistant coating layer comprising spherical inorganicparticles (A) having an average particle diameter of 3 to 50 micrometersand a Knoop hardness of at least 1,300 kg/mm², and a binder (B)comprising a crosslinkable resin comprising at least 10% by weight of apolyether urethane (meth) acrylate represented by the following generalformula (2):

    CH.sub.2 ═C(R.sup.1)--COOCH.sub.2 CH.sub.2 --OCONH--X--NHCOO-- --CH(R.sup.2)--(CH.sub.2).sub.n --O--!.sub.m --CONH--X--NHCOO--CH.sub.2 CH.sub.2 OCOC(R.sup.1)═CH.sub.2( 2)

wherein R¹ and R² each represent hydrogen or a methyl group, X is adiisocyanate radical, n is an integer of 1 to 3, and m is an integer of6 to 60, the average molecular weight of crosslinked molecules of saidbinder (B) after curing being from 200 to 800, the amount of saidspherical particles (A) being from 5% to 50% by weight of the totalamount of the components (A) and (B), the hardness of said sphericalparticles (A) being higher than that of said binder (B), the averageparticle diameter d, in micrometers, of said spherical particles (A)fulfilling the following inequality (1):

    0.3t≦d≦3.0t                                  (1)

wherein t is an average thickness, in micrometers, of said coatinglayer.